Spatial variability in the ionosphere measured with GNSS networks

Traveling ionospheric disturbances (TIDs) appear as medium-scale TIDs at midlatitudes and as polar cap patches at high latitudes. Both can have a negative impact on Global Navigation Satellite Systems (GNSS) measurements, although the amplitude is of tenths of a total electron content unit (TECU), 1 TECU = 1016 el m2. Due to their spatial extension, they affect GNSS measurements using receivers separated with distances up to ~1000 km.We present statistical measures of the ionospheric spatial variability as functions of time in solar cycle, annual season, and time of day for different geographical locations in Europe. In order to perform this spatial characterization of the ionosphere, we have used archived GPS data from a 13 year period, 1999–2011, covering a complete solar cycle. We find that the ionospheric spatial variability is larger for the northern areas than for the southern areas. This is especially pronounced at solar maximum. For the more northern areas, the ionospheric variability is greater during nighttime than during daytime, while for central Europe, the variability is larger during daytime. At solar maximum, the variability is larger during the months October and November and smaller in June and July.

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